import os
import sys
from unittest import skipIf

from django.core.exceptions import SuspiciousFileOperation
from django.core.files.base import ContentFile
from django.core.files.storage import FileSystemStorage, Storage
from django.db.models import FileField
from django.test import SimpleTestCase


class AWSS3Storage(Storage):
    """
    Simulate an AWS S3 storage which uses Unix-like paths and allows any
    characters in file names but where there aren't actual folders but just
    keys.
    """
    prefix = 'mys3folder/'

    def _save(self, name, content):
        """
        This method is important to test that Storage.save() doesn't replace
        '\' with '/' (rather FileSystemStorage.save() does).
        """
        return name

    def get_valid_name(self, name):
        return name

    def get_available_name(self, name, max_length=None):
        return name

    def generate_filename(self, filename):
        """
        This is the method that's important to override when using S3 so that
        os.path() isn't called, which would break S3 keys.
        """
        return self.prefix + self.get_valid_name(filename)


class GenerateFilenameStorageTests(SimpleTestCase):
    def test_storage_dangerous_paths(self):
        candidates = [
            ('/tmp/..', '..'),
            ('/tmp/.', '.'),
            ('', ''),
        ]
        s = FileSystemStorage()
        msg = "Could not derive file name from '%s'"
        for file_name, base_name in candidates:
            with self.subTest(file_name=file_name):
                with self.assertRaisesMessage(SuspiciousFileOperation, msg % base_name):
                    s.get_available_name(file_name)
                with self.assertRaisesMessage(SuspiciousFileOperation, msg % base_name):
                    s.generate_filename(file_name)

    def test_storage_dangerous_paths_dir_name(self):
        file_name = '/tmp/../path'
        s = FileSystemStorage()
        msg = "Detected path traversal attempt in '/tmp/..'"
        with self.assertRaisesMessage(SuspiciousFileOperation, msg):
            s.get_available_name(file_name)
        with self.assertRaisesMessage(SuspiciousFileOperation, msg):
            s.generate_filename(file_name)

    def test_filefield_dangerous_filename(self):
        candidates = ['..', '.', '', '???', '$.$.$']
        f = FileField(upload_to='some/folder/')
        msg = "Could not derive file name from '%s'"
        for file_name in candidates:
            with self.subTest(file_name=file_name):
                with self.assertRaisesMessage(SuspiciousFileOperation, msg % file_name):
                    f.generate_filename(None, file_name)

    def test_filefield_dangerous_filename_dir(self):
        f = FileField(upload_to='some/folder/')
        msg = "File name '/tmp/path' includes path elements"
        with self.assertRaisesMessage(SuspiciousFileOperation, msg):
            f.generate_filename(None, '/tmp/path')

    def test_filefield_generate_filename(self):
        f = FileField(upload_to='some/folder/')
        self.assertEqual(
            f.generate_filename(None, 'test with space.txt'),
            os.path.normpath('some/folder/test_with_space.txt')
        )

    def test_filefield_generate_filename_with_upload_to(self):
        def upload_to(instance, filename):
            return 'some/folder/' + filename

        f = FileField(upload_to=upload_to)
        self.assertEqual(
            f.generate_filename(None, 'test with space.txt'),
            os.path.normpath('some/folder/test_with_space.txt')
        )

    @skipIf(sys.platform == 'win32', 'Path components in filename are not supported after 0b79eb3.')
    def test_filefield_awss3_storage(self):
        """
        Simulate a FileField with an S3 storage which uses keys rather than
        folders and names. FileField and Storage shouldn't have any os.path()
        calls that break the key.
        """
        storage = AWSS3Storage()
        folder = 'not/a/folder/'

        f = FileField(upload_to=folder, storage=storage)
        key = 'my-file-key\\with odd characters'
        data = ContentFile('test')
        expected_key = AWSS3Storage.prefix + folder + key

        # Simulate call to f.save()
        result_key = f.generate_filename(None, key)
        self.assertEqual(result_key, expected_key)

        result_key = storage.save(result_key, data)
        self.assertEqual(result_key, expected_key)

        # Repeat test with a callable.
        def upload_to(instance, filename):
            # Return a non-normalized path on purpose.
            return folder + filename

        f = FileField(upload_to=upload_to, storage=storage)

        # Simulate call to f.save()
        result_key = f.generate_filename(None, key)
        self.assertEqual(result_key, expected_key)

        result_key = storage.save(result_key, data)
        self.assertEqual(result_key, expected_key)